Conventionally, when chamfering a corner part where an outer circumferential surface of a three-dimensional cam such as a cylindrical cam intersects the side surface of a cam groove formed there, a method of simultaneously forming the chamfered part at the left and right sides of the cam groove and a method of forming it one side at a time are known. As the former method, there are known a method of simultaneously forming a cam groove and chamfered part using a dedicated tool having a blade part having an outer shape equal to the width of the cam groove and a chamfering blade part expanding conically from the blade part and, for example, as disclosed in PLT 1, a method of forming the cam groove, then chamfering it using a dedicated tool having a chamfering blade part expanding conically from the width of the cam groove. As a method of forming one side at a time, for example, the method described in PLT 2 is known. There, the groove is formed, and then is chamfered using a conical tool having an outside diameter smaller than the groove.
A cam groove may also be chamfered not by using a machine tool, but manually using a file. According to this, there is no need to prepare a dedicated tool or an NC program for chamfering.